The finned tube heat exchanger is the most powerful assistant of the finned tube, but not all heat exchange occasions are suitable for using the finned tube heat exchanger.
When the heat transfer coefficients of the inner and outer sides of the tube are equal, the finned tube may not be used. Heat exchangers, such as oil-oil, water-water, gas-gas heat exchange.
When the heat transfer film coefficients on both sides of the heat transfer surface are very different, it is suitable to use a finned tube heat exchanger, because at this time, the smaller side becomes the main aspect of controlling heat transfer.
When designing finned tube heat exchangers, the heat transfer coefficient on the smaller side should be maximized. It is best to make the film coefficients on both sides roughly the same, which is mainly more favorable.
The methods of increasing the film coefficient of finned tube heat exchanger mainly include the following aspects;
1. Reduce the cross-sectional area of the passage to increase the flow rate, add baffles in the passage or promote the degree of turbulence, generally used in the tube structure of the finned tube heat exchanger.
2. Adding fins on the tube wall can not only increase the degree of turbulence, but also increase the heat transfer area. The main heat transfer function of the finned tube heat exchanger is based on this.
3. Use enhanced heat transfer surfaces, such as grooved surfaces of various shapes, or porous surfaces, which can obtain a considerable heat transfer film coefficient for heat transfer processes with phase changes such as condensation and boiling.
Although this kind of enhanced heat transfer reduces the consumption of metal, it also increases the processing difficulty and production cost, so it is rarely used in finned tube heat exchangers unless there is a specific installation space limitation.